Brush seals are typically employed for sealing between stationary and rotary components, e.g. packing about a rotary shaft in a power generation system, such as but not limited to gas turbines and steam turbines, and between high and low pressure regions on opposite sides of the seal. Conventional bristle packs particularly in high temperature environments require precise placement of super alloy bristles while maintaining tight tolerances.
Metallic brush seals in contact against uncoated rotors undergo severe wear if the rotor incursions are beyond 20 mils. Uncoated rotors undergo wear, generate a rough surface, and in turn cause more wear on the bristles in the brush assembly.
In the past, hard smooth wear resistant coatings such as CrC—NiCr or CrC—NiCr—Ag—CaF2BaF2 have been applied to rotors to address the wear on the bristles in the brush assembly. The hard smooth wear resistant coatings polish the bristles instead of wearing away the bristles. When working with brush seal assembly wear issues in the field, an entire rotor in a gas turbine or steam turbine would have to be removed and brought in to a shop to re-apply the wear resistant coatings. Additionally, accommodating large rotors in a small spray cell to apply the wear resistant coatings may pose significant difficulties.
Therefore, a self-lubricating brush seal assembly and a method of reducing air leakage in a power generation system that do not suffer from the above drawbacks is desirable in the art.